DESCRIPTION

Modifies the index or directory cache. Each file mentioned is updated
into the index and any unmerged or needs updating state is
cleared.

See also git-add(1) for a more user-friendly way to do some of
the most common operations on the index.

The way git update-index handles files it is told about can be modified
using the various options:

OPTIONS

--add

If a specified file isn’t in the index already then it’s
added.
Default behaviour is to ignore new files.

--remove

If a specified file is in the index but is missing then it’s
removed.
Default behavior is to ignore removed file.

--refresh

Looks at the current index and checks to see if merges or
updates are needed by checking stat() information.

-q

Quiet. If --refresh finds that the index needs an update, the
default behavior is to error out. This option makes
git update-index continue anyway.

--ignore-submodules

Do not try to update submodules. This option is only respected
when passed before --refresh.

--unmerged

If --refresh finds unmerged changes in the index, the default
behavior is to error out. This option makes git update-index
continue anyway.

--ignore-missing

Ignores missing files during a --refresh

--cacheinfo <mode> <object> <path>

Directly insert the specified info into the index.

--index-info

Read index information from stdin.

--chmod=(+|-)x

Set the execute permissions on the updated files.

--assume-unchanged

--no-assume-unchanged

When these flags are specified, the object names recorded
for the paths are not updated. Instead, these options
set and unset the "assume unchanged" bit for the
paths. When the "assume unchanged" bit is on, git stops
checking the working tree files for possible
modifications, so you need to manually unset the bit to
tell git when you change the working tree file. This is
sometimes helpful when working with a big project on a
filesystem that has very slow lstat(2) system call
(e.g. cifs).

This option can be also used as a coarse file-level mechanism
to ignore uncommitted changes in tracked files (akin to what
.gitignore does for untracked files).
You should remember that an explicit git add operation will
still cause the file to be refreshed from the working tree.
Git will fail (gracefully) in case it needs to modify this file
in the index e.g. when merging in a commit;
thus, in case the assumed-untracked file is changed upstream,
you will need to handle the situation manually.

--really-refresh

Like --refresh, but checks stat information unconditionally,
without regard to the "assume unchanged" setting.

--skip-worktree

--no-skip-worktree

When one of these flags is specified, the object name recorded
for the paths are not updated. Instead, these options
set and unset the "skip-worktree" bit for the paths. See
section "Skip-worktree bit" below for more information.

-g

--again

Runs git update-index itself on the paths whose index
entries are different from those from the HEAD commit.

--unresolve

Restores the unmerged or needs updating state of a
file during a merge if it was cleared by accident.

--info-only

Do not create objects in the object database for all
<file> arguments that follow this flag; just insert
their object IDs into the index.

--force-remove

Remove the file from the index even when the working directory
still has such a file. (Implies --remove.)

--replace

By default, when a file path exists in the index,
git update-index refuses an attempt to add path/file.
Similarly if a file path/file exists, a file path
cannot be added. With --replace flag, existing entries
that conflict with the entry being added are
automatically removed with warning messages.

--stdin

Instead of taking list of paths from the command line,
read list of paths from the standard input. Paths are
separated by LF (i.e. one path per line) by default.

--verbose

Report what is being added and removed from index.

-z

Only meaningful with --stdin; paths are separated with
NUL character instead of LF.

--

Do not interpret any more arguments as options.

<file>

Files to act on.
Note that files beginning with . are discarded. This includes
./file and dir/./file. If you don’t want this, then use
cleaner names.
The same applies to directories ending / and paths with //

Using --refresh

--refresh does not calculate a new sha1 file or bring the index
up-to-date for mode/content changes. But what it does do is to
"re-match" the stat information of a file with the index, so that you
can refresh the index for a file that hasn’t been changed but where
the stat entry is out of date.

For example, you’d want to do this after doing a git read-tree, to link
up the stat index details with the proper files.

Using --cacheinfo or --info-only

--cacheinfo is used to register a file that is not in the
current working directory. This is useful for minimum-checkout
merging.

To pretend you have a file with mode and sha1 at path, say:

$ git update-index --cacheinfo mode sha1 path

--info-only is used to register files without placing them in the object
database. This is useful for status-only repositories.

Both --cacheinfo and --info-only behave similarly: the index is updated
but the object database isn’t. --cacheinfo is useful when the object is
in the database but the file isn’t available locally. --info-only is
useful when the file is available, but you do not wish to update the
object database.

Using --index-info

--index-info is a more powerful mechanism that lets you feed
multiple entry definitions from the standard input, and designed
specifically for scripts. It can take inputs of three formats:

mode SP sha1 TAB path

The first format is what "git-apply --index-info"
reports, and used to reconstruct a partial tree
that is used for phony merge base tree when falling
back on 3-way merge.

mode SP type SP sha1 TAB path

The second format is to stuff git ls-tree output
into the index file.

mode SP sha1 SP stage TAB path

This format is to put higher order stages into the
index file and matches git ls-files --stage output.

To place a higher stage entry to the index, the path should
first be removed by feeding a mode=0 entry for the path, and
then feeding necessary input lines in the third format.

The first line of the input feeds 0 as the mode to remove the
path; the SHA1 does not matter as long as it is well formatted.
Then the second and third line feeds stage 1 and stage 2 entries
for that path. After the above, we would end up with this:

Using “assume unchanged” bit

Many operations in git depend on your filesystem to have an
efficient lstat(2) implementation, so that st_mtime
information for working tree files can be cheaply checked to see
if the file contents have changed from the version recorded in
the index file. Unfortunately, some filesystems have
inefficient lstat(2). If your filesystem is one of them, you
can set "assume unchanged" bit to paths you have not changed to
cause git not to do this check. Note that setting this bit on a
path does not mean git will check the contents of the file to
see if it has changed — it makes git to omit any checking and
assume it has not changed. When you make changes to working
tree files, you have to explicitly tell git about it by dropping
"assume unchanged" bit, either before or after you modify them.

In order to set "assume unchanged" bit, use --assume-unchanged
option. To unset, use --no-assume-unchanged.

The command looks at core.ignorestat configuration variable. When
this is true, paths updated with git update-index paths... and
paths updated with other git commands that update both index and
working tree (e.g. git apply --index, git checkout-index -u,
and git read-tree -u) are automatically marked as "assume
unchanged". Note that "assume unchanged" bit is not set if
git update-index --refresh finds the working tree file matches
the index (use git update-index --really-refresh if you want
to mark them as "assume unchanged").

forces lstat(2) to set "assume unchanged" bits for paths that match index.

mark the path to be edited.

this does lstat(2) and finds index matches the path.

this does lstat(2) and finds index does not match the path.

registering the new version to index sets "assume unchanged" bit.

and it is assumed unchanged.

even after you edit it.

you can tell about the change after the fact.

now it checks with lstat(2) and finds it has been changed.

Skip-worktree bit

Skip-worktree bit can be defined in one (long) sentence: When reading
an entry, if it is marked as skip-worktree, then Git pretends its
working directory version is up to date and read the index version
instead.

To elaborate, "reading" means checking for file existence, reading
file attributes or file content. The working directory version may be
present or absent. If present, its content may match against the index
version or not. Writing is not affected by this bit, content safety
is still first priority. Note that Git can update working directory
file, that is marked skip-worktree, if it is safe to do so (i.e.
working directory version matches index version)

Although this bit looks similar to assume-unchanged bit, its goal is
different from assume-unchanged bit’s. Skip-worktree also takes
precedence over assume-unchanged bit when both are set.

Configuration

The command honors core.filemode configuration variable. If
your repository is on a filesystem whose executable bits are
unreliable, this should be set to false (see git-config(1)).
This causes the command to ignore differences in file modes recorded
in the index and the file mode on the filesystem if they differ only on
executable bit. On such an unfortunate filesystem, you may
need to use git update-index --chmod=.

Quite similarly, if core.symlinks configuration variable is set
to false (see git-config(1)), symbolic links are checked out
as plain files, and this command does not modify a recorded file mode
from symbolic link to regular file.

The command also looks at core.trustctime configuration variable.
It can be useful when the inode change time is regularly modified by
something outside Git (file system crawlers and backup systems use
ctime for marking files processed) (see git-config(1)).